Cell-Types-and-Modifications.ppt

Lesson 1.2. Cell Types and Modifications  Learning Objectives At the end of this session: 1.i must be able to classify different cell types (plant/animal tissues) and specify the function(s) each (STEM_BIO11/12-Ia-c-3). 2.i must be able to describe some cell modifications that lead to carry...

Lesson 1.2. Cell Types and Modifications  Learning Objectives At the end of this session: 1.i must be able to classify different cell types (plant/animal tissues) and specify the function(s) each (STEM_BIO11/12-Ia-c-3). 2.i must be able to describe some cell modifications that lead to carry out specialized functions, such as cilia, flagella, microvilli, trichomes, root hair (STEM_BIO11/12-Ia-c-5)  What are Tissues?  A group of cells having common origin, similar structure and performing a definite function  Are plant and animal tissues the same?  plant tissues are different from animal tissues in many ways. What are the plant tissues? What are the animal tissues? Human Tissues  Cell Modifications  Some of the cell surfaces are modified for adaptive purposes.  These includes: Cilia  Flagella Microvilli Trichomes root hairs.  Cilia  Cilium (singular)  Slender protuberances that project from the much larger cell body  2 Types  Motile cilia – present on cell’s surface in large number and beat in coordinated waves. Example: lining of trachea and fallopian tubes  Non motile cilia –Example: sensory organs like eyes and nose  Functions of cilia In humans Mechanoreceptors. Example: lining of kidney tubules that monitor the flow of fluid through tubules Chemoreceptors – detect odors Photoreceptors – outer segment of the rods in the retina In protists such as Paramecium  for locomotion (through liquids)  Flagella  Tail-like projection that protrudes from the cell body of prokaryotic and eukaryotic and functions in locomotion  Types of flagellation  Based on the location of the bacteria 1.Monopolar – flagellum at one end 2.Bipolar – flagella are at both ends 3.Peritrichous – flagella are around the bacterial cell Flagella vs Cilia  Though eukaryotic flagella and motile cilia are ultrastructurally identical, the beating pattern of the two organelles can be different. In the case of flagella (e.g. the tail of a sperm) the motion is propeller-like. Beating of motile cilia consists of coordinated back-and- forth cycling of many cilia on the cell surface  Microvilli  Are microscopic cellular membrane that increase the surface area of some epithelial cells.  absorption  Examples: Small intestinal Kidney proximal tubule. In sensory cells of the inner ear (as stereocilia), In the cells of taste buds.  Functions of Microvilli Absorption in intestine  Secretion Trichomes  From a Greek word, means a growth of hairs and many of the appendages do in fact ressemble in appearance of the hairs of mammals.  Its size, shape and structure depend upon their function, eg. absorption, protection, support.  This image: two types, multicellular and glandular trichomes (secretes substance, eg. Smell of the plant)  Root Hairs  Extension of an epidermal cells of roots  increase the surface area of the root  increase the absorptive area of roots for absorption of water and nutrients from the soil  Little function in anchorage as they are delicate